System for controlling reciprocating motors



Aug. 12, 1930. c. s. WEYANDT SYSTEM FOR CONTROLLING RECIPROCATING MOTORS Filed May 13, 1924 'III I IIIIIIIA III/Ill,

INVENTOR 6:0" B

ATTORNEY Patented Aug. 12, 1930 UNITED STATES PATENT OFFICE CARL S. WEYANDT, OF PITTSBURGH, PENNSYLVANIA, ASBIGNOR TO CENTRAL ELEC- TRIC TOOL COMPANY, A CORPORATION OF PENNSYLVANIA Application filed m 13,

This invention relates to energy translating apparatus and particularly to electromagnets employed to do useful work.

This application is, in part, a continuation of application Serial N 0. 527,037, filed J anuary 4, 1922.

One object of my invention is to provide a novel method of and means for controlling an electro-magnet, and particularly to cause it to operate as a reciprocating motor and particularly to operate as a percussive tool or electric hammer.

A further object of my invention is to provide a control system for a tool of the above indicated character in which an electric valve is employed to transmit electrical impulses to the operating winding of the tool, thereby obviating the disadvantage inherent in a system including switching devices comprising separable contact members.

A furtherobject of my invention is to provide a control system for a percussive tool of the above indicated character in which the operation of the electric valve is controlled in accordance with the operation of the percussive tool.

In the electric hammer which I employ and control in accordance with the principles of my invention, I provide a barrel or equivalent of nonmagnetic material as a guide for a core in a solenoid which constitutes the actuating winding of the motor or hammer. In order to reduce the reluctance of the magnetic circuit, and to concentrate the magnetic flux developed by the actuating winding, I provide a plurality of laminations of substantially C-shape comprising two end port-ions separated to form an air gap. The laminations are disposed around the solenoid, or winding, with the air gap adjacent the side of the barrel and opposite the middle region of the winding. The tips determiningthe air gap, extend through openings in the barrel to within a few thousandths of an inch from the inner surface of the barrel engaged by the moving core. By reason of the tips being disposed very close to the core, leakage flux is reduced to a minimum and substantially the complete magnetic flux is concentrated upon the core to actuate it in either direction. With 1924. Serial No. 712,917.

this construction the efficiency of the motor is considerably increased over that heretofore attained.

It has been customary, heretofore, to use switching devices for supplying current im-- pulses to the operating windings of electric hammers to procure a reciprocating movement of the core. By reason of the value of current transmitted, arcing between the contact surfaces has always necessitated giving considerable care and attention to the switchmg devices.

An object of my invention has been to obviate the disadvantages inherent in a system em-' ploying switching devices to control the operation of an electric hammer. Instead of a switching device, embodying separable contact surfaces susceptible to arcing, I provide an electric valve comprising stationary terminals, an anode and a cathode, respectively, for controlling the energization of the hammer operating winding. A field-producing element, such as a winding surrounding the bulb containing the electrodes, serves to control the current transmission between the two electrodes by properlv controlling the conductivity between the electrodes. The transmission of current between the electrodes may be controlled to transmit current impulses to the hammer to effect its operation in such broadly similar system comprising a recip-.

rocating motor provided with an auxiliary winding for controlling application of current to the motor. I do not claim the subject matter disclosed in that application, but claim more specific subject matter of the character herein disclosed. In the present invention I utilize the auxiliary winding of an electric hammer of the character referred to for controlling the energization of the field: producing element associated with an electric valve. The field-producing element is consequently energized in accordance with the movement of the coremember of the hammer and operates to control the valve accordingly. If the core lags behind its normal speed, a current impulse of longer duration is transmitted to the hammer, whereas if the core leads its normal operating speed the duration of the transmitted current impulse is reduced.

When the valve is employed to control the energization of an electric hammer from an alternating current circuit, Wlll automatically transmit current wave impulses of one polarity or the other depending upon the manner in which it is connected between the circuit and the hammer. Under such circumstances the field-producing element will control the duration of the transmitted impulse which will include the current transmitted through the valve by reason of the mpressed voltage and also the current resulting from the restoration of the energy stored in the magnetic field of the hammer winding. hen the hammer is energized from an alternating current circuit, the current impulse transmitted by the valve will resemble, to some extent, one wave of a sinusoidal current. When the current value decreases to zero the value will, of course, transmit no current until the next current wave of the same polarity traverses the circuit.

When a valve is employed to control the energization of the hammer from a direct current circuit, there is no inherent tendency of the current to decrease to zero value, but, nevertheless, inasmuch as the circuit between the electrodes may readily be rendered nonconductive by the field-producing element, the disadvantages of arcing between contact surfaces are obviated. The energization of the field-producing element under such circumstances may similarly be controlled by an auxiliary winding on the hammer. unit, or it may be controlled by an external contact device, inasmuch as the energizing current necessary for the field-producing element is relatively small and the current carrying burden placed upon the contacting device will be inappreciable.

When the hammer is energized from an al- I ternating current circuit, its speed or frequency of operation will depend upon the frequency of the current of the supply circuit. When the hammer is energized from a direct current circuit, its speed or frequency of operation will depend upon the magnetic force developed by the operating winding, the time constant of that winding and the mass of the core that is to be actuated thereby, if the auxiliary winding of the ham mer is employed to control the valve. If,

' however, an external contacting device is em- 1ployed to control the energization of the old-producing element, the speed of the hammer will depend upon the speed or frequency of operation of the contacting device. Under such circumstances, the design of the hammer will depend upon the nature of the work to which it is to be ap lied and the speed of operation best suited or such work. The characteristics of the operating winding and the'mass of the core will depend upon the speed at which the hammer is to be operated. The length of the stroke of the core will also depend upon the speed at which the hammer is to be operated, the greater the speed, the shorter the stroke, and vice versa. In any of the systems that are employed in which a valve is used to transmit the main operating current, the disadvantages of separable contact members in a. circuit transmitting relatively large currents are obviated.

A better understanding of the invention may be had upon reference to the accompanying drawings in which Fig. 1 is a longitudinal view partially in section and partially in elevation of an electric hammer;

Fig. 2 is a diagrammatic view of an electrical circuit illustrating the system which I employ to control the operation of the hammer as illustrated in Fig. 1.

Fig. 3 is a diagrammatic view of a modiiied electrical circuit for controlling the energization of the motor from a direct current circuit; and

Fig. 4 is a graph'illustrating the form of the current impulse transmitted to the hammer by the electric valve.

As illustrated in Fig. 1, the electric hammer 10 comprises a main or actuating winding 11, a core member 12 responsive thereto and controlled thereby to do useful work, and an auxiliary or secondary winding 13 disposed adjacent the main winding 11 and the core 12, to'be inductively influenced in accordance with the energization of the main winding 11 and the movement of the core 12.

The hammer further comprises a barrel or guide 14: of non-magnetic material to retain the core in a predetermined path of movement. A plurality of iron laminations 15 are disposed around the main winding 11 and adjacent the barrel 14 to provide a short air ga within which the auxiliary winding 13 is isposed. A front end plate 16 is disposed on and secured to the front end of the barrel 14 and accommodates a tool bushing 17 which holds a tool 18 in the path of travel of the core 12 in its forward movement. A back end plate 19 and'a handle 20 integral therewith are secured to the rear end of the barrel 14 and cooperate therewith to hold a spring-controlled backstop or bumper 21 in position in the path of travel of the core 12 in its backward movement. An enclosing shell or casing 22 surrounds the electro-magnet structure and is held in position by the front'and the back end plates 16 and 19.

A triggerswitch 23 is disposed in the handle of the hammer and is sub ect to control by the operator for initiating and stopping operation of thehammer. The laminations are rovided with tips or tenons 24 that fit tightly in apertures in the barrel 14 and serve to secure the winding in position. All of the air gaps between the tips 24 together constitute an annular air gap which is bridged or shunted by the core in its reciprocating movement.

As illustrated in Figi2, energy for operating the hammer 10 is derived rom an alternating current circuit 30 and transmitted through an electric valve 31. The electric valve 31 here illustrated is of the electronic type comprising an electron-emitting element or filament 32 as a cathode, and a split cylindrical plate 33 as an anode, both of which are enclosed in an evacuated vessel 34.

A field-producing element or winding 35 is disposed-around the vesseland, when sufiiciently energized, serves to prevent electron conduction between the cathode 32 and the anode. 33. The field-producing element 35 is connected to the auxiliary winding 13 of the hammer 10. Energy for exciting the filament 32 to render it incandescent and electron-emitting is derived from the circuit 30 through the medium of a transformer '36.

When operation of the hammer is desired, the trigger switch 23 is closed. A magnetic switch 37 is thereupon energized to connect one terminal of the main winding 11 to the plate or anode 33, the other terminal of the hammer winding 11 being connected to conductor 38 of the circuit 30. The filament 32 is connected to conductor 39 of circuit 30 and when the polarity of circuit 30 is such that the filament 32 is negative with respect to the plate 33, current will traverse the circuit including the filament and plate of the valve and the main winding of the hammer. For the sake of simplicity it may be consid ered that the valve is so connected as to trans mit what will be termed the positive current waves to the hammer winding.

When a current wave impulse is transmitted to the hammer through the valve, the core is actuated in one directioiror the other by the main winding 11 and as it approaches the air gap the transformer action between the main winding 11 and the auxiliary Winding 13 increases. When the core reaches or bridges the air gap maximum transformer action obtains, and the auxiliary winding is energized to a maximum degree. Consequently, the field-producing element 35 associated with the valve is correspondingly energized. Electron conduction between the filament and the plate is thereupon so controlled as to prevent current conduction therebetween and the further energization of the main winding of the hammer from the I or frequency main circuit 30 is, eluded. The core tmues on its for the time being, premember meanwhile conpath of travel to engage the tool to do useful work, if actuated in a forward direction, or, if actuated in a backward'direction, to engage the backstop and store its kinetic energy therein until again actuated in a forward direction.

The auxiliary winding, being disposed adjacent theair gap, is subjected to the maximum change of magne 'c flux in response to the decreased reluctance of the magnetic circuit as the core approaches the air gap. The electro-motive force induced in the auxiliary Windingis therefore an accurate indication of the operation of the hammer and of the location of the c05 member at or with relation to the air gap during its travel. By means of such electro-motive force, the valve 31 may be properly controlled to temporarily preclude further energization of the main wlnding from the circuit. Thus, when sufficient energy has been stored in the core to actuate it in one direction or another the operating winding is immediately de-energized to permit the core to pass the air gap so that it will complete its stroke and not be held there to complete the magnetic circuit of the hammer.

As soon as the main winding is de-energized, the auxiliary winding is, of course, also immediately de-energized. The conductivity of the valve is immediately re-established when the crcuit attains the proper polarity. A current impulse is thereupon again transmitted by the valve to energize the mainwinding of the hammer and the same controlling operation is again-effected by means of the auxiliary winding 13 to energize the fieldproducing element of the valve. The speed of operation of the hammer when controlled as illustrated in Fig. 2 will be half the frequency of the current derived from the circuit 30. For example, if the circuit 3O is'a source of 60 cycle current the hammer will operate at the rate of 30 strokes per second. i

A further idea of the operation of the hammer may be derived from a consideration of the wave form illustrated in Fig. 4. If for any reason the core member lags in its operation, as might be caused by starting friction, due to improper lubrication or to dust between the core and the barrel, a

greater intervalof time will elapse betweenthe instant when current is transmitted to the winding and the instant when the core shunts the air gap. The transmitted wave will consequently be of longer duration and the base line of the current wave impulse illustrated in Fig. 4 will be relatively long.' If, by reason of the rebound after impact with the tool or the backstop, the core member tends to lead its normal speed, it will ap proach the air gap more quickly and the cutof! opiaration of the valve will be eifected current wave impulses of such character as are imminently necessary to efiect the operation of the core. The operation is entirely automatic and controlled in accordance with the instant operating demand of the hammer.

A stem of this ,character thus resents the afi vantages of automatic contro of the electric valve in accordance with the operation of the hammer, and also the advanta es of a control circuit in which no separa 1e contact surfaces are present between which arcin might occur.

In ig. 3 is illustrated a for controlling an electric hammer. The system illustrated has particular utility when employed to control the energization of the motor from a direct current circuit. In the system illustrated in Fig. 3, energy is derived from a direct current circuit and supplied to the hammer 10 through an electric valve of the same type as illustrated in Fig. 2. Instead of controlling the fieldproducin element 35 in response to a condition obtaining in the hammer itself, however, an external switching device 51 is used to control the circuit of the field-producing element. The switching device 51 comprises a motor 52, which may be of a variable speed type, if desired, and a rotary switch 53 controlled by the motor. The switch 53 energizes the field-producing element associated with the electric valve at a frequency depending upon the speed of the motor 52.

A resistor 54 is employed to provide a source of relatively low potential difference for-energizing the filament of the electric valve 31.

The operation of the hammer in this system is similar to that in the system illustrated in Fig. 2. When operation of the hammer is desired, the trigger switch 23 is closed. The magnetic switch 37 is, energized to connect one terminal of the hammer winding 11 to the plate or anode 33 of the valve, the other terminal of the winding being connected to conductor 55 of the circuit 50. The filament 32 of the valve is so connected to the resistor 54 that the conductor 56 of negative polarity, constitutes one terminal to which the filament is connected. When the hammer winding 11 is connected to the anode by the magnet switch 37 an energy impulse is transmitted by the valve to ener ze the windin and actuate the core mem er. The duration of the im ulse transmitted by the 'valve de ends upon e duration of the intervals of modified circuit gagement between the contacting surfaces of the rotary switch 53 that is dnvenby the ing. When the field-producing element is energized, the valve is rendered non-conduc- "tive and the hammer winding is de-ener- 'gized. Since each impulse transmitted by the valve actuates the core member in one direction or the other, the core member may be caused to reciprocate at any predetermined speed as controlled by the operation of the motor 52 in energizing and de-energizing the fieldroducing element associated with the electric valve.

By means of a system of the present charactor for controlling an electric hammer especially. when energlzed from a source of direct current, an e ectric valve of the type employed resents the advantages of simplicity and reliability. Ordinarily a rupture of a direct current of any appreciable value involves considerable arcing. The value of the current necessary to operate an electric hammer of the type here illustrated requires a current of the order of six to eight amperes.

The rupture of a current of this value several thousand times perminute would seriously affect the surfaces of engaging contact members. By means of a valve of the character here employed, however, the currents may be easily and readily ruptured without any detrimental efi'ects.

Since the field-producing element associated with the valve requlres a relatively small current to establish a controlling field for'the valve, the burden placed upon the rotary switch 53 in rupturing the circuit of the field controlling element is small and the incidental arcing is inappreciable.

My invention thus comprehends the employment of an electric valve for controlling the energization of a reciprocating motor from an alternating current circuit or from a direct current circuit, and the control of the electric valve either automatically, in response to a condition of the hammer, or by some external means. The feature of my invention is the utilization of the electric valve provided with a field-controlling element which may be controlled in any desired manner to control the operation of the=reciproeating motor. V 4

My invention is not limited to the specific arrangement of the elements as illustrated in the systems shown in the accompanying drawings but may be variously modified without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim:

1. Reciprocating motor mechanism comprisin% an operating winding an aperiodic movab e member responsive thereto, a unidevice controllin said source to said winding and comprlsmg lateral current-transmitting device comprising a cathode and an anode for supplying a predominatingly uni-directional current to the operating winding, and means responsive to a redetermined movement of the movable member for controlling the operation of the current-transmitting device.

2. The combination with a reciprocating motor com rising an operating winding an an a erio ic movable member reciprocated there y, of a source of current, an impedance other than that of said operating winding variable in magnitude between finite limits controlling the delivery of current from said source to said winding, and means varying the magnitude of said impedance in response to movement of said reciprocating member.

3. The combination with a reciprocatin motor comprising an operating winding an a-reciprocating member controlled thereby, of a source of current, a current-transmitting delivery of current from electrodes spaced from each other to form a conductive path means for producing a magnetic field 1n the space between said electrodes, and means influenced by movement of said reci rocating member controlling said fieldro ucin means.

4. he com ination with a reciprocating motor comprising an operating winding and a reciprocating member for oing external mechanical work controlled thereby, of a source of current, a thermionic impedance controlling delivery of current from said source to said winding, and means for varying the magnitude of said impedance in responseto c ange in magnitude of the ma netic flux produced by said operating win 1n The combination with a reciprocating motor embodyin an operating winding and a movable mem r actuable thereby, of a magnetron for transmitting current to the winding comprising a closed vessel containing a cathode and an anode an external winding for controlling current conduction therebetween, and an auxiliary winding associated with the operating winding of the motor for energizing the external winding of the magnetronto control the supply of current to the motor.

6. The combination with a reciprocating motor comprising an actuating winding and a reciprocating member controlled thereby,

' of a source of alternating current, a rectifier controlling transmission to said winding from said source of preponderatingly unidirectional current impulses and including an impedance variable between finite limits while passing current to said winding, and

means controlling the magnitude of the impedance of said rectifier in response to change in magnitude of magnetic flux produced by said wlnding.

7. The combination with a reciprocatin motor comprising an operating winding am a reciprocating member controlled thereby, of a source of alternating current, an as metrical conductor whose impedance w ile conducting. is variable in magnitude and controls delivery of preponderatingly unidirectional current impulses from said source to said winding, and means responsive to change by said reciprocating member of the magnitude of magnetic flux produced by said impedance.

8. The combination with a reciprocatin motor comprising an operating winding and a reciprocating member controlled thereby, of a source 0 alternating current, a thermionic impedance controlling delivery of preponderatingly uni-directional current impulses from said source to said winding, and means responsive to changes in magnitude of magnetic flux in the field produced by said winding for varying the magnitude of said thermionic impedance.

9. The combination with a reciprocating motor comprising a winding and a reciproeating member controlled thereby, of a source of alternating current, a thermionic impedance controlling delivery of peponderatingly uni-directional current impulses from said source to said winding, means for inducing electro-motive-force in response to changes in magnetic flux in the ma netic circuit of said winding, and means su jected to said induced electro-motive-force controlling the magnitude of said thermionic impedance.

10. The combination with a reciprocatin motor comprising an actuating winding an an aperiodic movable member, and a source of energy therefor, of current-transmitting means between the source of energy and the motor, comprising an electronic device, and means influenced by the current passed through said device to the motor for controlling the operation of the electronic device.

11. The combination with a reciprocating motor comprising an actuating winding and an aperiodic movable member for doing external mechanical work, and a source of energy therefor, of current-transmitting means between the source of energy and the motor comprising an electronic device, and means of said reciprocatin member within a stroke thereof for diminishing the current existing in said windin during that stroke.

13. The combination with a reciprocating motor com rising a winding and a reciproeating mem er controlled thereby, of a source of alternating current, an impedance variable in magnitude between finite limits while current is passing through said winding for controlling delivery of spaced current impulses from said source to saidwinding, and means responsive to change of magnetic flux in the field of said winding during a stroke of said reciprocating member for varyin the magnitude of said impedance and contro lling the duration of the current impulse transmitted within that stroke to said winding from said source.

14. The combination with a reciprocating motor comprising a reciprocating member and an operating winding surrounding said member, of a source of current, a thermionic impedance controlling delivery of current from said source and variable in magnitude while current is passing through said winding, and acoil inductively related to said solenoid and through which said member reciprocates to control the magnitude of said impedance.

15. The combination with a reciprocating motor comprising an operating winding, an auxiliary winding inductively related to said operating winding, fixed magnetizable members spaced to form an air gap providing magnetic leakage path for transformer comprising said windings, and a movable member controlled by said operating winding reciprocable through said windings and said air gap to do external mechanical work and to vary the voltage induced in said auxiliary winding, of a source of current, a thermionic impedance controlling delivery of current from said source intermittently to energize said winding, and means influenced by current induced in said auxiliary winding to vary the magnitude of said impedance.

16. The combination with a reciprocating motor comprising an operating winding, an auxiliary winding inductively related to said operating winding, fixed magnetizable members spaced to form an air gap providing magnetic leakage path for transformer comrising said windings, and a movable memer controlled by said operating winding reciprocable through said windings and said air gap to do external mechanical work and to vary the voltage induced in said auxiliary winding, of a source of current, a thermionic impedance controlling delivery of current from said source intermittently to energize said winding, and means including said auxiliary wlnding responsive to movement of said movable member within a stroke there-- of to reduce to zero. value the current 'in'said operating winding during that stroke.

there y, of a source of current, an electric valve, and means varying the impedance of said valve within finite limits in response to movement of said reciprocating member for controlling delivery of current from said source to said winding.

18. The combination with a reciprocatin motor comprising an operating winding and an aperiodic movable member reciprocated there'y, of a source of current, an electric valve for delivering spaced current impulses from said source to said winding, and means for varying the duration of said impulses passed through said valve in accordance with the movement of said reciprocating member.

19. The combination wlt-h ercussive tool comprising an operating windin and a striking element actuated thereby, o a source of alternating current, an electric valve for delivering spaced current impulses from said source to said winding, and means for varying the duration of said impulses passed through said valve in accordance with the movement of said striking element.

20. The combination with percussive tool comprising an operating winding and a striking element actuated thereby, of a separate source of alternating current, an electric valve for delivering spaced current impulses from said source to said winding, and means for varying the duration of said impulses passed through said valve in accordance with the movement of said striking element.

21. In combination with a reciprocating motor mechanism comprising an operating winding and an aperiodic movable member power current, an asymmetrically conducting current-transmitting device comprising an anode and cathode intervening between said source of current and said operating winding for transmitting to said winding preponderatingly uni-directional current impulses for actuating said aperiodic movable member at a frequency dependent upon the frequency of said source, and means comprising an auxiliary winding inductively related to said operating winding for controlling the impedance between said anode and cathod, and thereby modifying the duration of the current impulses transmitted through said operating winding.

22. The combination with a reciprocating motor comprising an operating winding and an aperiodic movable member reciprocated thereby, of a source of alternating power current, and asymmetrically conducting impedance intervening between said source of power current and said operating winding for selecting from said source preponderatingly un-directional impulses and for impressing said impulses upon said winding to actuate saidmovable member at a frequency dependent upon the frequency of the alternating power current and means responsive to movement of sai aperiodic movable member for varying the magnitude of said impedance within finite limlts.

' for actuating said operating member at a frequency dependent upon the frequency of said source, an auxiliary winding inductively related to said operating winding, and means influenced by said auxiliary winding and disposed adjacent said electrodes for controlling the duration of said space current impulses.

24. In combination, a reciprocating motor comprising an actuating winding and an aperiodic movable member actuated thereby, a source of alternating power current, an electron discharge device intervening between said source of power and said actuating winding for selecting from said source and impressing upon said winding. preponderatingly uni-directional current impulses for actuating said aperiodic movable member at a frequency dependent upon the frequency of said source, and means influenced by the movement of said aperiodic movable member for modifying the impedance of said electron discharge device for modifying the duration of said impulses.

25. The combination with motiveower apparatus including an aperiodic wor -producing element disposed for vibratory movement, an alternating-current supply circuit elcctro-magnetic means supplied from sai circuit and operable to impart such movement to said element at a frequency dependent upon the frequency of such supply, and valve means included in said circuit, of means influenced by current conditions in said electro-magnetic means for controlling valve action of said valve means.

26. The combination with motiveower apparatus including an aperiodic wor -producing element disposedfor vibratory movement, an alternating-current supply circuit, clectro-magnetic means supplied from said circuit and operable to impart such movement to said element at a frequency dependent upon the frequency of such supply, and valve means included in said circuit, of a winding inductively related to said electromagnetic means and influenced by virtue of such relation to control valve action of said valve means.

27. The combination with motive ower apparatus including an aperiodic wor -producing element disposed for vibratory ment, an alternating-current su ply circuit electro-ma netic means supplied from sai circuit an operable to impart such movement to saidelement at a frequency dependent upon the frequenc of such supply, and valve means include of means influenced by current conditions in said electro-magnetic means for controlling valve action of said valve means, said third-named means including field-producing means associated with said valve means.

movein said circuit,

28. In combination, a reciprocatin motor comprising a windin and a movab e member reci rocated there y, a source of current for sai winding, an impedance variable in magnitude between finite limits controlling the delivery of current from said source to said winding, and magnetic field-producing means for periodically varying the magnitude of said impedance.

In testimony whereof, I have hereunto subscribed my name this 29th da of April 1924.

- CARL s. bvEYANbT. 

